I en värld med ökande koldioxidhalter i atmosfären och höjd medeltemperatur, råder det inga tvivel om att vi står inför en rad utmaningar för att minska användandet av bland annat fossila bränslen som generar skadliga utsläpp. Det finns många alternativ till oljebaserade bränslen, och ett som har ökat markant de senaste åren är bränslepellets. Bränslepellets är ett träbaserat biobränsle som i sitt kompakta tillstånd erbjuder ett bra värmevärde och är klimatneutralt. För att tillverka pellets måste råmaterialet först termiskt torkas, från en fukthalt på ca 55 % till ca 10 %, vilket i dagsläget kan motsvara upp till en fjärdedel av hela energiåtgången i pelleteringsprocessen. Med den ökade efterfrågan av bränslepellets finns också ökade förutsättningar för energieffektiviseringar i pelletsproduceringen, speciellt i torkningssteget.   Drinor AB har tagit fram en avvattningsmaskin av biomaterial som heter CDP, och med den är det möjligt att avvattna biomaterial till ca 30 %, vilket skulle reducera både tiden och energin det tar att termiskt torka materialet. Avvattningen sker under tryck på minst 40 ton, där vattnet mekaniskt pressas ut ur råmaterialet. Hur avvattningen påverkar råmaterialet, speciellt i en pelletframställning, är oklart och syftet med detta arbete var att ta reda på hur pelleteringsegenskaperna påverkas efter pressning med CDP, och om det finns möjligheter att spara energi i malningsdelen i pelleteringsprocessen.   Målet med arbetet var att ta reda på hur CDP påverkar pelletskvaliteter i form av hårdhet och densitet, samt om friktionsutvecklingen i pelleteringsmatrisen förändras, genom att framställa pellets ur 3 scenarion. I ett scenario ska en traditionell pelletsframställning liknas, med endast termisk torkning och i de resterande två scenarion implementeras CDP som försteg till den termiska torkningen. I ett av dessa två scenarion mals inte träflisen innan pelletering, för att se om energi kan sparas utan att offra pelletskvalitet. Ett annat mål var att, per scenario, ta reda på vid vilken fukthalts- och temperaturkombination de bästa pelletsen tillverkades med avseende på hög densitet och hårdhet samt låg friktionsutveckling.   Resultaten visade att scenariot med CDP som komplement till termisk torkning och utan malningprocess, producerade pellets med högst hårdhet, högst densitet och lägst friktionsutveckling under båda fukthalterna på pelleteringsmaterialet och nästintill samtliga matristemperaturer. Det scenario som hade endast termisk torkning producerade pellets med lägst densitet och hårdhet samt högst friktion under nästan alla temperaturer och fukthalter.   När den bästa fukthalts- och temperaturkombinationen togs fram per scenario, så var scenariot med CDP och utan malning bäst. Pellets producerade där hade ökad densitet, nästan tredubblad hårdhet samt mer än halverad friktionsutveckling i pelleteringsmatrisen, jämfört med scenariot som imiterade traditionell pelletsframställning med endast termisk torkning.   Skulle det scenariot med CDP och utan malningsprocess implementeras i en verklig industriell skala skulle det innebära stora förutsättningar för ökad produktion av pellets med bättre kvalitet, samt ett minskat energianvändande i form av reducerad termisk torkning och minskat användande av malningsprocessen. / In a world with growing carbon dioxide contents in the atmosphere and elevated average temperature, there is no doubt that we are faced with a number of challenges to reduce the use of, among other things, fossil fuels that generate harmful emissions. There are many alternatives to oil-based fuels, and one that has increased markedly in recent years is fuel pellets. Fuel pellets are a wood-based biofuel that, in its compact state, offers a good thermal value and is climate neutral. In order to produce pellets, the raw material must first be thermally dried, from a moisture content of about 55 % to about 10 %, which can currently account for up to at least a quarter of the total energy consumption in the pelleting process. With the increased demand for fuel pellets, there are also increased possibilities for energy efficiency in the pellet production, especially in the drying stage.   Drinor AB has developed a biomaterial dewatering machine called CDP, with which it is possible to drain the biomaterial to a moisture content of about 30%, which would reduce both the time and the energy it takes to thermally dry the material. The dewatering pressure is at least 40 tonnes, where the water is mechanically squeezed out of the raw material. How the dewatering affects the raw material, especially in a pellet production, is unclear and the purpose of this work was to find out how the pelleting properties are affected after pressing with CDP and if there is potential for saving energy in the grinding process in the pelleting process.   The aim of the work was to find out how CDP affects pellet qualities in terms of hardness and density, and if the friction development in the pelleting dye changes, by making pellets out of 3 scenarios. In one scenario, traditional pellets production should be resembled, with only thermal drying, and in the remaining two scenarios, CDP is implemented as a complement to thermal drying. In one of these two scenarios, the wood chips were not milled before pelleting, to see if energy can be saved without sacrificing pellet quality. Another goal was to determine, by each scenario, what moisture and temperature combination the best pellets were produced with respect to high density and hardness and low friction development.   The results showed that the CDP scenario, as a complement to thermal drying and without grinding process, produced the hardest pellets, highest density and lowest friction development during both moisture levels of the pelleting material and almost all die temperatures. The scenario that only had thermal drying produced pellets with the lowest density and hardness, as well as maximum friction under almost all temperatures and moisture levels.   When the best moisture and temperature combination was achieved by each scenario, the scenario with CDP and without grinding was the best. Pellets produced there had increased density, almost triple the hardness, and more than half the friction development in the pelleting die, compared to the scenario that imitated traditional pellets production with only thermal drying.   Should the scenario with CDP and without grinding process be implemented on a real industrial scale, it would provide great conditions for increased production of better quality pellets, as well as reduced energy use in the form of reduced thermal drying and reduced use of the grinding process.

This master thesis deals with design of grate biomass boiler with 50 t/h power. A fuel of the boiler is a mixture of contaminated biomass and woodchips. The boiler produces steam with parameters of 4,2 MPa and 420 °C. Stochiometric and thermal calculations are based on given fuel composition and output steam parameters. Heat exchangers are designated in accordance with the calculations. General drawing of the boiler is attached to this document. Anti-corrosion measures are considered, due to chlorine content in biomass. Hydraulic and aerodynamic losses and dew point of the flue gas is calculated in the end.

This thesis describes the design of boilers for wood chips in a gas boiler house. Consisting of boiler house design from concept design suitable heat source to design components necessary for the proper functionality of the boiler house. Part of thesis is compilation of a functional diagram and design of possible solutions.

The Brista 1 plant is a wood chip-fired combined heat and power (CHP) plant located near Märsta, northwest of Stockholm, Sweden. The primary purpose of the plant is to supply heat to the northwest district heating grid. In order to meet increasing demand for district heating, Fortum Heat is constructing a second CHP plant next to Brista 1. The Brista 2 plant will use a mixture of municipal and industrial waste as fuel. Due to changes in the European Green Certificate program, the fuel subsidies for wood chips will be significantly reduced. This will cause the Brista 1 plant to incur significantly increased operating costs. The Brista 2 plant, however, will not be affected by these changes and will therefore be much cheaper to run than Brista 1. However, due to the large demand for district heating it will be necessary to run both plants in parallel at certain times in order to meet the heating demand and/or maximize revenue during periods of high electricity demand. A computer program has been constructed using MATLAB which simulates the Brista 1 and 2 plants and their combined operation in both backpressure and direct condensing mode. The results show that the optimum allocation of heat production does not seem to be affected by electricity price assuming both plants are operated in backpressure mode. The reason for this would seem to be that the production costs (fuel, emissions, O&M) are unaffected by the electricity price. Therefore, the allocation which maximizes electrical power production, and thus revenue from electricity sales, will always be favored. In certain cases, it is more profitable to run the Brista 1 plant in direct condensing mode. The reason for this would seem to be that the thermal efficiency is somewhat higher, and that at low electricity prices the revenues from electricity sales do not offset the cost of the reduced heat production.

La gazéification de biomasse lignocellulosique en biogaz fait partie des technologies attractives permettant de s’affranchir des énergies fossiles et de valoriser les déchets agricoles ou forestiers. Néanmoins, le développement de cette technologie est freiné par son rendement énergétique faible et la production de polluants (CO2, NOx…). La pyrolyse/gazéification par voie solaire permettrait alors de pallier certains de ces inconvénients (énergie propre et gratuite, process à haute température produisant moins de polluants). Dans ce contexte, l’objectif de cette thèse est de développer une approche expérimentale et numérique afin de maîtriser les procédés de pyrolyse/gazéification de copeaux de bois pour mieux appréhender le développement de la gazéification solaire. D’abord, un travail détaillé de caractérisation des copeaux de bois a été réalisé, alliant diverses analyses des échantillons mais aussi des analyses basées sur l’utilisation d’images tomographiques au rayon X pour déterminer les propriétés morphologiques et, par simulation numérique, les propriétés effectives de transport des copeaux de bois. Ensuite, des essais avec un four-réacteur à échelle laboratoire ont été réalisés pour étudier le séchage, la pyrolyse et la gazéification des copeaux de bois. Ces essais nous ont permis d’étudier l’influence de paramètres comme la température en séchage et en pyrolyse ou le débit de vapeur d’eau en gazéification. En parallèle, un modèle multi-physique pour la simulation de la pyrolyse a été développé. Cet outil a permis une étude détaillé des phénomènes mis en jeu et, in fine, permettrait d’optimiser le système. Enfin, le design d’un gazéifieur solaire a été réalisé. / Thermochemical conversion of lignocellulosic biomass belongs to attractive technologies which are viable routes to reduce reliance on fossil energy and to enhance carbon conversion efficiency. Nevertheless, classical gasification process via autothermal combustion of biomass presents severe drawbacks as bad yield and produced important pollutants. Solar concentrated energy enables high temperature reactions with reduced contaminating gas and higher yield. In this context, this thesis aims at developing experimental and numerical approaches to study detailed mechanism of pyrolysis and gasification processes of wood chips packed bed which are key step toward designing efficient solar gasifier. In a first time, inner properties of wood (initial composition and thermal decomposition) were studied via ultimate and proximate analyzes. Structural and morphological properties of wood chips were computed using image analysis. Effective mass and heat transport properties of the packed bed were assessed via direct numerical simulation combined with X-ray tomographic images. Then a laboratory scale device enabling to characterize pyrolysis and gasification kinetics and gas production was developed. The aim of this experimental work was to understand the impact of parameters such as drying and pyrolysis temperatures, and the steam flow rate during gasification. A multiphysical model of pyrolysis of wood chips packed bed was also developed. It allowed to perform detailed study of pyrolysis physics and in fine it will allow optimizing the pyrolysis/gasification process. Finally, a first design for a solar gasifier was reported and constitutes the basis of further studies.

One of the major cost factors in mechanical pulp production is the electrical energy input. Much of the research in this field has therefore been devoted to an understanding of the mechanisms in the refining process and, consequently, to find ways of reducing the electrical energy consumption. Shear and compression are probably the main types of fibre deformation occurring in refiners for collapsing and fibrillating the fibres into a suitable pulp. In current refiners, the repeated mechanical action of the bars on the fibres consumes large amounts of energy in a treatment of mechanical fibres that is almost random. Fundamental studies of the deformation of wood have indicated that a combination of shearing and compression forces is highly beneficial in terms of fibre deformation with a low energy demand. Pure compression is able to permanently deform the fibre but requires a substantial amount of work, while pure shearing, although being much less energy demanding, does not lead to any permanent deformations. A more suitable application of the shear and compression forces on the wood fibres during the refining process could be a way to develop fibres at a lower energy demand. These ideas have been studied in this work trying to find new ways of saving energy in the mechanical pulping process. The first paper in this thesis discusses the way of producing wood shavings and the introduction of shear/compression deformations in these, as well as the potential benefits of using them instead of wood chips as raw material for TMP production. With the shaving process, high deformations in the wood cells were achieved by the shear and compression forces. This led to energy savings of about 25% at a given tensile index, when compared to traditional chips. The quality of the pulp produced from wood shavings was found to be better than that of the pulp produced from wood chips, when it came to strength properties (except for tear index) and optical properties at comparable energy levels. Another way of reducing energy consumption in refining involving a limited shear combined with compression forces for the mechanical treatment of both wood chips and coarse fibres was also studied. This work shows that such a kind of treatment resulted in a high degree of fibre collapse at low energy demands. The thick-walled transition fibres could even be permanently deformed. Furthermore, refining trials, utilising shear and compression pre-treated chips, showed that the strength properties, except for tear index, along with the optical properties of a TMP could be improved and the electrical energy consumed could be reduced by approx. 100 kWh/tonne, when compared to untreated chips. The results from the pilot trials described in this work could be used as a starting point for further implementation in the industry, in order to identify the most efficient way of producing mechanical pulp with a lower consumption of electrical energy. / QC 20101119

Material degradation and a decrease of fuel quality are common phenomena when storing biomass. A magnitude of 7.8% has been reported to degrade over five months when storing spruce wood chips in the winter in Central Europe. This thesis presents a theoretical study of biomass storage. It includes investigations of bio-chemical, chemical and physical processes that occur during storage of chipped woody biomass. These processes lead to degradation caused by micro-activity, chemical oxidation reactions and physical transformation of water. Micro-activity was modeled with Monod kinetics which are Michaelis-Menten type of expressions. The rate expressions were complemented with dependency functions describing the impact of oxygen, moisture and temperature. The woody biomass was divided into three fractions. These fractions represent how hard different components of the wood are to degrade by microorganisms. Chemical oxidation was modeled as a first order rate expression with respect to the active components of the wood. Two different cases have been simulated during the project. Firstly, an isolated system with an initial oxygen concentration of air was considered. This case displayed a temperature increase of approximately 2˚C and a material degradation less than 1%. The second case considered an isolated system with an endless depot of oxygen. This case resulted in degradation losses around 0.45-0.95% in the temperature range between 65-80˚C during approximately 300 days of storage. The temperature increased slowly due to chemical oxidation.

Intresset för biobränsleproducerad energi har ökat i takt med att kunderna blivit mer miljömedvetna. På grund av detta har efterfrågan på briketter ökat samtidigt som träindustrin har haft det svårt i en sviktande konjunktur. Därför har ett examensarbete utförts i samarbete med E.ON Värme Sverige AB där undersökningar på bränslebyte i pannor avsedda för torra bränslen till fuktigare, stamvedflis har utfört. För denna undersökning har begränsningar införts på övre och undre effekt i form av uppehållstid och slutförbränningstemperatur. Intervallen är enbart beräknade på stamvedflis med 30 och 40 % fukthalt. Undersökning visar att det går bra att elda stamvedsflis i briketteldade pannor utan att emissionerna ökar så pass mycket att villkoren för anläggningarna överskrids om lasten hålls inom vissa intervall. Det möjliga effektintervallet ökar med minskad fukthalt på bränslet. Undersökningen har visat att det är bränslets kvalitet som är den mest begränsande faktorn. / The interest in bioenergy has increased with increased environmental awareness. The increasing demand on biofuels and the decreasing availability of the rawmaterials for making refined biofuels such as wood briquettes and wood pellets have caused the prices of these biofuels to increase. This report is performed in collaboration with E.ON Värme Sverige AB and its purpose is to investigate the possibilities for a change of fuels in existing boilers designed for refined biofuels, from wood briquettes to wood chips. To be able to calculate a power interval where it would be possible to use wood chips with moisture contents of 30 and 40% by weight respectively, we had to make some assumptions regarding maximum flue gas flow, minimum retention time and the lowest temperature regarding complete combustion of CO. Our calculations show that it is possible to use woodchips with a moisture content of 30 % w/w without any significant problems in all our boilers. When the moisture content is increased to 40 % w/w the interval for possible power output becomes more narrow. The amount of dust that is being emitted from the boilers does not exceed the limits regulated by environmental law, unless the thermal load of the boiler is too high. The single most important factor for a successful change of fuel from wood briquettes to woodchips is that the fuel quality is good.

<p>Intresset för biobränsleproducerad energi har ökat i takt med att kunderna blivit mer miljömedvetna. På grund av detta har efterfrågan på briketter ökat samtidigt som träindustrin har haft det svårt i en sviktande konjunktur. Därför har ett examensarbete utförts i samarbete med E.ON Värme Sverige AB där undersökningar på bränslebyte i pannor avsedda för torra bränslen till fuktigare, stamvedflis har utfört.<strong></strong></p><p>För denna undersökning har begränsningar införts på övre och undre effekt i form av uppehållstid och slutförbränningstemperatur. Intervallen är enbart beräknade på stamvedflis med 30 och 40 % fukthalt.</p><p>Undersökning visar att det går bra att elda stamvedsflis i briketteldade pannor utan att emissionerna ökar så pass mycket att villkoren för anläggningarna överskrids om lasten hålls inom vissa intervall. Det möjliga effektintervallet ökar med minskad fukthalt på bränslet.</p><p>Undersökningen har visat att det är bränslets kvalitet som är den mest begränsande faktorn.</p> / <p>The interest in bioenergy has increased with increased environmental awareness. The increasing demand on biofuels and the decreasing availability of the rawmaterials for making refined biofuels such as wood briquettes and wood pellets have caused the prices of these biofuels to increase. This report is performed in collaboration with E.ON Värme Sverige AB and its purpose is to investigate the possibilities for a change of fuels in existing boilers designed for refined biofuels, from wood briquettes to wood chips.</p><p>To be able to calculate a power interval where it would be possible to use wood chips with moisture contents of 30 and 40% by weight respectively, we had to make some assumptions regarding maximum flue gas flow, minimum retention time and the lowest temperature regarding complete combustion of CO.</p><p>Our calculations show that it is possible to use woodchips with a moisture content of 30 % w/w without any significant problems in all our boilers. When the moisture content is increased to 40 % w/w the interval for possible power output becomes more narrow. The amount of dust that is being emitted from the boilers does not exceed the limits regulated by environmental law, unless the thermal load of the boiler is too high.</p><p>The single most important factor for a successful change of fuel from wood briquettes to woodchips is that the fuel quality is good.<strong></strong></p>

This thesis deals with design of hot water grate boiler, where the output is water with parameters 130 °C and pressure 16 bar. In the content of the whole thesis is gradually introduced a stoichiometric calculations, which is based on the specified fuel – wood chips. This is followed by the design of the individual heating surfaces according to the thermal calculations given in the thesis. Finally, the calculation is extended by hydraulic and aerodynamic losses. Dimensional design, as a basic scheme, is shown at thesis. More detailed drawing documentation is attached to this thesis.